a. Field of the Invention
This invention relates to methods for making bicomponent polyester filaments having improved bulk potential.
b. Description of the Prior Art
The primary purpose of producing a bicomponent filament is to provide a filament which, when properly treated, will be self-crimping to give added bulk to yarns made from the filament. It has been found that certain bicomponent polyester filaments spun at relatively slow speeds and oriented in a separate operation by drawing the filaments 4.5 to 5.5.times.over a heated draw pin will have reasonably good bulkiness when subjected to a boiling water treatment. However, this process is undesirable from an economic standpoint for the reasons that the production rate is relatively low, additional energy is required to heat the filament and a separate operation is usually required. It has been found that the increasing of spinning speeds in such an operation, in order to increase productivity, usually results in a reduced bulk potential in the finished yarn.
In the process of the present invention, significantly higher spinning speeds can be used to produce bi-component filaments having excellent bulk potential by drawing bicomponent filaments of polyethylene terephthalate and polybutylene terephthalate at about room temperature in a zone isolated from the spinning zone. Substantially higher spinning rates have been achieved and the filaments produced have good bulk potential.